Some tutorials are for the Casbin's model and work for all Casbin implementations in different languages. Some other tutorials are language-specific.
This paper digs deeply into the design details about Casbin. Please cite the following BibTex if you use Casbin/PML as a reference in your paper:
@article{luo2019pml, title={PML: An Interpreter-Based Access Control Policy Language for Web Services}, author={Luo, Yang and Shen, Qingni and Wu, Zhonghai}, journal={arXiv preprint arXiv:1903.09756}, year={2019} }